Antilymphocyte antibodies (ALA) occur in patients with systemic lupus (SLE) and a significant number of their blood and non-blood relatives. These antibodies have also been implicated in the defect in immunoregulation found in SLE. We are studying the interaction of ALA with lymphocytes. We hope to isolate ALA specific for discrete lymphocyte surface antigens and determine how they affect lymphocyte and monocyte function. The first set of ALA under investigation are those specific for B2-microglobulin. We are also exploring the interaction between prostaglandin E2 inhibition of lymphocytes and ALA.